NSInvocation调用

CurrentDate.h

#import <Foundation/Foundation.h>


@interface CurrentDate : NSObject {
    
}
- (NSString *) stringForDate: (NSDate *)date 
              usingFormatter: (NSDateFormatter *)formatter;

@end

CurrentDate.m

#import "CurrentDate.h"


@implementation CurrentDate

- (NSString *) stringForDate: (NSDate *)date 
              usingFormatter: (NSDateFormatter *)formatter
{
    return [formatter stringFromDate: date];
}

@end

main.m

#import <Foundation/Foundation.h>
#import "CurrentDate.h"

//参考：http://theocacao.com/document.page/264
int main (int argc, const char * argv[])
{

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    //原始调用
    NSDateFormatter * dateFormat = [[NSDateFormatter alloc] 
                                    initWithDateFormat:@"%b %d %Y" 
                                    allowNaturalLanguage: NO];
    CurrentDate * currentDateClassObject = [[CurrentDate alloc] init];
    NSString * currentDate = [currentDateClassObject 
                              stringForDate: [NSDate date] 
                              usingFormatter: dateFormat];
    NSLog(@"currentDate: %@", currentDate);
    
    
    //NSInvocation调用
    SEL mySelector = @selector(stringForDate:usingFormatter:);
    NSMethodSignature * sig = [[currentDateClassObject class] 
                               instanceMethodSignatureForSelector: mySelector];
    
    NSInvocation * myInvocation = [NSInvocation invocationWithMethodSignature: sig];
    [myInvocation setTarget: currentDateClassObject];
    [myInvocation setSelector: mySelector];
    
    NSDate * myDate = [NSDate date];
    [myInvocation setArgument: &myDate atIndex: 2];
    
    NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateStyle: NSDateFormatterMediumStyle];    
    [myInvocation setArgument: &dateFormatter atIndex: 3];
    
    NSString * result = nil;    
    [myInvocation retainArguments];    
    [myInvocation invoke];
    [myInvocation getReturnValue: &result];
    NSLog(@"The result is: %@", result);
    

    [pool drain];
    return 0;
}